1. Field of the Invention
The invention relates to an ink jet printer, and more particularly to an ink jet printer for forming an image on a recording medium by irradiation of ultraviolet rays after jetting ultraviolet curable ink.
2. Description of the Related Art
Recently, an ink jet printer that is an image recording apparatus adopting an ink jet recording method, has been widely used, because it can simply produce images at a low cost, compared with methods needing plate making such as a gravure printing method and a flexography printing method.
In a field where ink jet printers are used for recording images on products or wrapped products, non-ink-absorptive material, such as resin and metal, is frequently used for product itself or for wrapping products. As an ink jet printer for fixing ink on such non-ink absorptive material as a recording medium, there has been known such an ink jet printer that uses ultraviolet curable ink (refer, for example, JP-Tokukaisho 60-132767).
The ink jet printer using ultraviolet curable ink usually irradiates ultraviolet curable ink jetted on the recording medium to cure the ultraviolet curable ink for fixing it on the recording medium. At this time, it is preferable to irradiate ultraviolet rays as soon as possible after the impact of the ultraviolet curable ink, because, if it takes time to irradiate ultraviolet rays after the impact of the ultraviolet curable ink on the recording medium, such problems remarkably arise in expansion of a dot diameter of ink jetted on the recording medium, bleeding of ink between contiguous dots, and soaking of the ink into the recording medium.
A serial type ink jet printer generally records an image by jetting the ink from the jet openings of recording heads with the heads mounted on a carriage moving in a scanning direction. For avoiding the above-mentioned problems, the ink jet printer is usually provided with an ultraviolet irradiating device at downstream side of the recording heads in the scanning direction on the carriage so that the irradiating device can move together with the recording heads on the carriage. With this structure, the ultraviolet rays can be irradiated to the ink jetted from the heads just after the impact on the recording medium, thereby avoiding the problems described above.
The ink jet printer described above usually performs maintenance on the recording heads so as to recover from clogging at jet openings due to increase of ink viscosity or adhered ink, or clogging inside ink flow channels due to bubbles or contaminants, or to fill the recording heads with ink.
The above-described ink jet printer has a maintenance unit disposed at a predetermined maintenance region within a carriage scanning area for performing the head maintenance. Therefore, during image forming when the head maintenance is not needed, the carriage sometimes comes into the maintenance region and the ultraviolet irradiating device irradiates the maintenance unit.
Irradiation of ultraviolet rays on the maintenance unit is possible to cause deterioration of component parts such as an absorbing device and a wiping device constructing the maintenance unit. Further, the ultraviolet curable ink sticking to the component parts, for example, the absorbing device and the wiping device of the maintenance unit is cured by the irradiation of ultraviolet rays, which may reduce head maintenance performance, leading to unsuccessful head maintenance.